Height exceptions. With the exception of residential uses as permitted by this chapter, penthouses or roof structures for the housing of stairways, tanks, ventilating fans, air-condition equipment or similar equipment required to operate and maintain the building, skylights, spires, cupolas, flagpoles, chimneys or similar structures may be erected above the height limits prescribed by this chapter but in not case more than 25% more than the maximum height permitted for the use in the district, or 10 feet, whichever is less.